1. Field of the Invention
The present invention generally relates to coupling mechanisms and more particularly, to a king pin coupling mechanism in which a king pin secured to a trailer vehicle is brought into or out of engagement with a fifth wheel member of a tractor vehicle.
2. Description of the Prior Art
Conventionally, in king pin coupling mechanisms, it has been so arranged as shown in FIGS. 1 to 3 that a pair of locking jaws 1 are pivotally supported by a pair of pins 2, respectively, while an engaging piece 3 having a guide rod 15 secured thereto is urged towards a king pin 5 by a spring 4 wound around the guide rod 15 so as to be inserted between head portions 1a of the locking jaws 1. Meanwhile, the guide rod 15 is slidably fitted into a guide hole 7 formed in an outer peripheral rib 6 of a main plate 16 supported on a body of a tractor vehicle (not shown). Furthermore, a lever 8, which extends through a recess 11 of the engaging piece 3 as shown in FIG. 2, has a pivotal pin 9 provided at one end thereof and a grip portion 10 formed at the other end thereof. Moreover, as shown in FIG. 3, a stopper 13 is pivotally supported so as to be pivoted about a pin 12 by a wire 14 attached to the stopper 13. Then, operations and safety of the prior art king pin coupling mechanisms referred to above will be described, hereinbelow. When the king pin 5 is in its coupling position as shown in FIG. 1, the stopper 13 covers the guide hole 7 as shown in FIG. 3 so as to prevent the guide rod 15 from projecting out of the guide hole 7. In order to release the king pin 5 in the coupling position, the wire 14 is initially pulled in the direction of the arrow of FIG. 3, so that the stopper 13 is displaced to a position shown by the imaginary lines of FIG. 3 and thus, the guide hole 7 is exposed, whereby the guide rod 15 is allowed to project out of the guide hole 7. Subsequently, when the grip portion 10 is displaced in the direction of the arrow of FIG. 1, the engaging portion 3 in engagement with the lever 8 is also displaced together with the lever 8 in the direction of the arrow of FIG. 1. Consequently, the engaging piece 3 is disengaged from the head portions 1a of the locking jaws 1, whereby it becomes possible to release the king pin 5 from the locking jaws 1. Since a mechanism for holding the lever 8 and the engaging piece 3 in this state is well known, description thereof is abbreviated.
However, the prior art king pin coupling mechanisms have such an inconvenience that, when a single operator operates them so as to disengage the king pin 5 from the locking jaws 1, he is required to operate the lever 8 by one hand while pulling the wire 14 by the other hand, which is extremely difficult.
Furthermore, the known king pin coupling mechanisms have such a disadvantage that, since the pin 12, stopper 13 and wire 14 are provided outside the outer peripheral rib 6 of the main plate 16, there is a strong possibility of damage thereto. Especially, in the case where the tractor and trailer vehicles run along a curve, the wire 14 is readily cut upon its contact with the bodies of the vehicles, thereby resulting in a fatal accident upon disconnection of the trailer vehicle from the tractor vehicle. Thus, the prior art king pin coupling mechanisms are undesirable from the standpoints of operational efficiency and safety.